This project aims to elucidate the mechanisms by which the cell exerts control over the metabolism of fatty acids, complex lipids and the overall lipid composition of the cell membrane and outer layers. Regulatory mechanisms governing biosynthesis of the lipid components of the envelopes of procaryotic organisms as model systems will be emphasized. Several different approaches will be employed. The first is the study of regulatory mutants of lipid metabolism in Escherichia coli and other unicellular true bacteria. The lesions of regulatory mutants of E. coli now in hand will be determined by study of the enzymes presumably involved as the sites of genetic lesion, and by mapping the mutations by reference to known genetic markers. The second approach is a continuation of a comparative study of microorganisms to uncover and characterize any repression and/or feedback inhibition of fatty acid and/or lipid biosynthesis by fatty acids or complex lipids that occurs. A third approach involves study of the occurrence and synthesis of lipids in the blue-green algae. This group of procaryotic organisms has been so far only poorly studied, and exhibits a number of unique features (e.g., a high and varied cellular content of polyunsaturated fatty acids) which suggest singular value as models for study of regulation.